Although the term biodrainage is relatively recent, the concept is not new. The drainage of waterlogged land through the introduction or modification of vegetation has been practised historically in different parts of the world.
The increasing concern about the environmental impact of intensive agricultural development and associated monocultures has resulted in increased interest in the use of trees and salt-tolerant crops as an integrated part of the landscape and farming on saline land. The concept of the multi-use of trees as drainage providers, biodiversity ameliorators and productive crops is gaining wider acceptance.
CONCLUSIONS
Waterlogging: Biodrainage can effectively contribute to strongly reducing the problems as experienced from waterlogging in irrigated agriculture and non-irrigated agriculture.
Salinization: The problems associated with a rise in salinity in the rootzone can be effectively delayed using biodrainage systems in semi-arid and arid areas.
Positive aspects of biodrainage systems may be summarized as follows:
1. A more natural environmental setting is achieved in irrigated areas (projects).
2. A significant contribution is made to integrated rural development and the well-being of rural livelihoods.
3. Added advantages of biodrainage and bio-disposal systems, depending on the vegetation used, are: production of timber, fuel wood, oil, fruits, fibre, contribution to carbon sequestration, diminishing the effects of wind erosion, provision of shade and shelter, function as windbreaks, yield organic matter for fertilizer, enhancement of biodiversity, as flora and fauna flourishes, diminishing air pollution.
4. As compared to conventional subsurface drain-age systems, biodrainage systems perform the following four functions together:
Dewatering, i.e. inducing water flow through the soil towards a tubewell or pipe drain.
Transportation of the drain water to collector drains and thereafter to main drains.
Pump lifting effluent to higher levels in the evacuation system (as often required) and/or further conveyance by gravity outflow to disposal sites.
Final disposal at selected sites (e.g. by evaporation ponds).
5. Investment might be relatively low and could be borne by the farmer beneficiaries themselves. However, costs could be increased by fencing, wildlife protection, etc., depending on location.
Negative aspects of biodrainage systems may be summarized as follows:
1. require more land
2. are not very effective in removing salt
3. do not allow for controlled drainage
Biodrainage combined with conventional drainage systems combine positive and negative aspects as stated above: they are more positive and less negative than when only making use of conventional drainage systems. In general they should be preferred over strictly conventional drainage systems.
